Centurion transport reuses HID++ 2.0 feature IDs 0x0000, 0x0001,
0x0003, 0x0005, 0x0007 with different meanings. Since SupportedFeature
(IntEnum) requires unique values, create a separate CenturionCoreFeature
enum and resolve_feature() helper for transport-aware lookup.
Also replace the +0x100 offset hack in FeaturesArray.inverse with a
dedicated sub_inverse dict for sub-device feature indexing.
Move CenturionReceiver class, factory function, and Centurion protocol
queries (firmware, serial, hardware info, battery, name) from device.py
and hidpp20.py into new centurion.py module. Move OnboardEQ biquad math
and payload builders from hidpp20.py into new onboard_eq.py module.
Move _read_usb_product_string() to common.py to avoid circular imports.
Re-exports preserve backward compatibility for all existing callers.
Ken Sanislo